Structures for preventing cross-talk between through-silicon vias and integrated circuits

ABSTRACT

A semiconductor chip includes a through-silicon via (TSV), a device region, and a cross-talk prevention ring encircling one of the device region and the TSV. The TSV is isolated from substantially all device regions comprising active devices by the cross-talk prevention ring.

TECHNICAL FIELD

This invention relates generally to integrated circuits, and moreparticularly to structures and methods for reducing the cross-talksbetween through-silicon vias and integrated circuits in semiconductorchips.

BACKGROUND

Since the invention of integrated circuits, the semiconductor industryhas experienced continuous rapid growth due to constant improvements inthe integration density of various electronic components (i.e.,transistors, diodes, resistors, capacitors, etc.). For the most part,this improvement in integration density has come from repeatedreductions in minimum feature size, allowing more components to beintegrated into a given chip area.

These integration improvements are essentially two-dimensional (2D) innature, in that the volume occupied by the integrated components isessentially on the surface of the semiconductor wafer. Although dramaticimprovements in lithography have resulted in considerable improvementsin 2D integrated circuit formation, there are physical limitations tothe density that can be achieved in two dimensions. One of theselimitations is the minimum size needed to make these components. Also,when more devices are put into one chip, more complex designs arerequired.

An additional limitation comes from the significant increase in thenumber and length of interconnections between devices as the number ofdevices increases. When the number and length of interconnectionsincrease, both circuit RC delay and power consumption increase.

Among the efforts for resolving the above-discussed limitations,three-dimensional integrated circuit (3DIC) and stacked dies arecommonly used. Through-silicon vias (TSV) are often used in 3DIC andstacked dies for connecting dies. In this case, TSVs are often used toconnect the integrated circuits on a die to the backside of the die. Inaddition, TSVs are also used to provide short grounding paths forgrounding the integrated circuits through the backside of the die, whichis typically covered by a grounded metallic film.

FIG. 1 illustrates a stacked die structure with die 10 stacked on die12, wherein dies 10 and 12 are electrically connected through solderballs 16. Die 12 includes TSVs 14, which extend all the way from theback surface (facing top) to the front surface (facing down) of die 12.TSVs 14 are further electrically connected to solder balls 18, which maybe used to mount the stacked die structure onto a package substrate or amotherboard. Through TSVs 14, die 10 can not only be connected to die12, but also to solder balls 18 directly.

TSVs 14 may be used as signal paths or grounding paths, and relativelygreat currents may be conducted through them. The currents flowingthrough TSVs 14 may thus have cross-talk with the integrated circuits indie 12. The cross-talk may become severe enough to cause noticeableperformance degradation in die 12, particularly if the integratedcircuits in die 12 include analog circuits, or the integrated circuitsare operated at high frequencies. Solutions are thus needed to at leastreduce the cross-talk.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a semiconductorchip includes a through-silicon via (TSV) and a cross-talk preventionring encircling one of a device region and the TSV. The TSV is isolatedfrom substantially all device regions comprising active devices by thecross-talk prevention ring.

In accordance with another aspect of the present invention, asemiconductor chip includes a seal ring comprising four sides, eachbeing adjacent to an edge of the semiconductor chip; and a cross-talkprevention ring encircled by the seal ring. The cross-talk preventionring includes four sides, each being adjacent to one of the sides of theseal ring. The cross-talk prevention ring is preferably grounded. Thesemiconductor chip further includes a TSV in a region between the sealring and the cross-talk prevention ring; and a device region encircledby the cross-talk prevention ring, wherein the device region comprisesactive devices.

In accordance with yet another aspect of the present invention, asemiconductor chip includes a seal ring comprising four sides, eachbeing adjacent to an edge of the semiconductor chip; and a seal ringextension comprising a first end and a second end, each physicallyconnected to a portion of the seal ring. The seal ring extension and theseal ring form a cross-talk prevention ring encircling a first region ofthe semiconductor die, wherein the first region is substantially freefrom active devices. The semiconductor chip further includes a TSV inthe first region; and a second region outside the cross-talk preventionring, wherein the second region comprises active devices.

An advantageous feature of the present invention includes reducedcross-talk between the cross-talk prevention ring and the integratedcircuit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a conventional stacked-die structure includingthrough-silicon vias;

FIGS. 2A and 2B are a top view and a cross-sectional view of anembodiment of the present invention, respectively, whereinthrough-silicon vias are formed between a seal ring and a cross-talkprevention ring;

FIGS. 3 through 5B are alternative embodiments of the present invention,wherein cross-talk prevention rings have different shapes;

FIG. 6 illustrates a cross-talk prevention ring comprising a portion ina semiconductor substrate;

FIGS. 7A and 7B are structures for performing simulations; and

FIG. 8 illustrates the simulation results, wherein the scatteringparameter is illustrated as a function of frequency.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

FIG. 2A illustrates a top view of a first embodiment of the presentinvention, which includes semiconductor chip (also referred to as die inthe packaging art) 20. Seal rings 24 and 26 are formed close to edges 21of chip 20. Seal rings 24 and 26 are preferably grounded. As is known inthe art, seal ring 26 is sometimes referred to as a main seal ring,while seal ring 24 is referred to as a sacrificial seal ring.Sacrificial seal ring 24 is optional.

Through-silicon vias 28 are formed in an inner region encircled by sealring 26. In an embodiment, TSVs 28 are located close to seal ring 26,and may be formed as a line along each side of seal ring 26.Correspondingly, TSVs 28 may have a ring-like structure. In thepreferred embodiment, the distance D2 between TSVs 28 and the respectiveside of seal ring 24 is small. One skilled in the art will realize thatthe dimensions recited throughout the description are merely examples,and may be scaled with the down-scaling of integrated circuits.

Cross-talk prevention ring 30 is formed in inner sides of TSVs 28, andis preferably signal grounded. Throughout the description, when aconductive feature, such as cross-talk prevention ring 30, is referredto as signal grounded, the conductive feature is connected either to theground, or a (high frequency) shield group, wherein signals(particularly high frequency signals) in the shield group are filtered.In either case, when signal grounded, the conductive feature issubstantially free of noise, particularly high frequency noise. A signalground is therefore defined as the ground or the shielded group that issubstantially noise free. Cross-talk prevention ring 30 is preferablyformed close to TSVs 28 and seal ring 24, so that the chip area used bythe cross-talk prevention structures is minimized. Similarly, thedistance D3 between TSVs 28 and the respective sides of cross-talkprevention ring 30 is preferably small. The inner region 32 enclosed bycross-talk prevention ring 30 is a device region, in which activedevices such as transistors (symbolized by transistor 31 in FIG. 2B) areformed. Device region 32 may include analog circuit region 32 ₁, digitalcircuit region 32 ₂, and combinations thereof.

In the preferred embodiment, the region 29 between cross-talk preventionring 30 and seal ring 26 is free from active devices. Alternatively,some low frequency digital devices, which are less prone to thecross-talk, are formed in region 29, while analog devices and/or highfrequency devices are not in region 29.

FIG. 2B illustrates a cross-sectional view of the structure shown inFIG. 2A, wherein the cross-sectional view is taken along line 2B-2B. Thecross-sectional view illustrates that TSVs 28 extend from the topsurface of chip 20 to the back surface. Bond pads 38 are formed on oneside of chip 20 and are electrically connected to TSVs 28. Bond pads 40may be connected to TSV 28 through redistribution lines 42, which arepreferably formed of copper, aluminum, and the like. Redistributionlines (not shown) may also be formed and connected to TSVs 28 and bondpads 38, so that bond pads 38 may be horizontally spaced apart from therespective TSVs 28.

Seal rings 24, 26, and cross-talk prevention ring 30 may be formedsimultaneously, each including a plurality of interconnected metal lines44 and vias 46. Each of the illustrated metal lines 44 and vias 46 mayform a ring encircling device region 32. Preferably, contact plugs 48,which are also preferably rings, are formed in inter-layer dielectric(ILD) 49, which is over semiconductor substrate 52. Contact plugs 48 areelectrically connected to the respective overlying metal lines 44 in thebottom metallization layer. Also, aluminum pad 50 may be formed as aring. Seal rings 24, 26, and cross-talk prevention ring 30 may each besignal grounded through bond pads 54. Alternatively, metal lines may beformed inside metallization layers to electrically connect seal rings24, 26, and cross-talk prevention ring 30 to other grounding paths.Cross-talk prevention ring 30 thus isolates TSVs 28 and device region 32from each other, so that the cross-talks between TSVs 28 and deviceregion 32 is reduced.

In an embodiment, substantially all TSVs in chip 20 are isolated fromdevice region 32 by cross-talk prevention ring 30. In alternativeembodiments, only a portion of TSVs that are expected to carry eitherrelatively high currents, or signals with high frequencies, are isolatedfrom device region 32 by cross-talk prevention ring 30, while remainingTSVs may be formed in device region 32.

FIG. 3 illustrates an alternative embodiment of the present inventionincluding a plurality of TSVs 28 and a plurality of cross-talkprevention rings 60. Each of the TSVs 28 may be encircled by one of thecross-talk prevention rings 60, which are preferably formedsimultaneously with seal rings 24 and 26. Similarly, cross-talkprevention rings 60 are also formed of interconnected metal lines, vias,contact plugs, aluminum pads, and the like. An advantageous feature ofthis embodiment is that TSVs 28 may be embedded inside device region 32.In addition, if some of the TSVs 62 are not expected to carry highcurrents and/or carry currents with high frequencies, these TSVs 62 donot necessarily need to be encircled by cross-talk prevention rings 60.

FIG. 4 illustrates a further embodiment, wherein TSVs 28 are enclosed bycross-talk prevention ring 66, which is signal grounded. However, notall sides of cross-talk prevention ring 66 are adjacent to a respectiveedge 21 of semiconductor chip 20. TSVs 28 and cross-talk prevention ring66 may thus be formed at locations other than edge regions ofsemiconductor chip 20.

In FIGS. 5A and 5B, the cross-talk prevention structures of TSVs 28 eachinclude seal ring extension 68 and a portion of the rectangular-shapedseal ring 26. Seal ring extension 68 is preferably formedsimultaneously, and thus has a similar layered structure, as seal ring26. This cross-talk prevention structure may also isolate TSVs 28 fromdevice region 32. In FIG. 5A, the cross-talk prevention structure isformed close to a corner of seal ring 26. In FIG. 5B, all TSVs 28 areformed close to one edge of chip 20, and seal ring extension 68 isformed as a straight line with two ends, each physically connected to aportion of seal ring 26.

It is realized that the structures shown in FIGS. 2 through 5B may becombined to provide better cross-talk preventing ability, and provideflexibility to the design. In addition, cross-talk prevention rings mayextend into the semiconductor substrates. In FIG. 6, conductive ring 70,preferably formed of metal, is formed in semiconductor substrate 52.Conductive ring 70 is preferably a metal ring, which may be formed oftungsten, aluminum, copper, and the like. Alternatively, conductive ring70 is a well region, preferably heavily doped by implanting a p-type orn-type impurity. In the preferred embodiment, conductive ring 70 adjoinscross-talk prevention ring 30, and hence is also grounded. Conductivering 70 acts as a sink for currents generated by the cross-talk.

Alternatively, instead of forming conductive ring 70, a dielectric ring72 is formed in semiconductor substrate 52. Dielectric ring 72 acts as abarrier for the cross-talk currents generated in substrate 52. Theformation of conductive ring 70 or dielectric ring 72 may includeetching semiconductor substrate 52 to form a trench ring, filling thetrench ring with a conductive material or a dielectric material, andperforming a chemical mechanical polish to remove excessconductive/dielectric material. The conductive ring 70 or dielectricring 72 may also be formed under cross-talk prevention rings 60 and 66as shown in FIGS. 3 and 4, respectively, and under seal ring extensions68 as shown in FIGS. 5A and 5B.

By forming the cross-talk prevention structure, the cross-talk issignificantly reduced. FIG. 7B illustrates a structure for performing asimulation, wherein port 1 is a signal input port, and port 2 is asignal output port. The grounded cross-talk prevention ring 80 encirclesport 1. The simulation results revealed that the scattering parameterS21, which is expressed as 20 log(V_(port) _(—) ₂/V_(port) _(—) ₁), issignificant reduced than if cross-talk prevention ring 80 does notexist, which structure is shown in FIG. 7A. The simulation results areshown in FIG. 8, wherein the scattering parameter S21 is illustrated asa function of frequency. Line 82 is the simulation result of thestructure shown in FIG. 7A, and line 84 is the simulation result of thestructure shown in FIG. 7B. It may be concluded that the cross-talk aremore severe at higher frequencies. However, regardless of thefrequencies, the cross-talk prevention structure may reduce thecross-talk by more than about 20 decibels.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

1. A semiconductor chip comprising: a through-substrate via (TSV)extending through a semiconductor substrate, the TSV being asignal-carrying TSV; a device region; and a cross-talk prevention ringcomprising a first portion in a metallization layer over thesemiconductor substrate, the first portion encircling the device region,wherein the TSV is isolated from substantially all device regionscomprising active devices by the cross-talk prevention ring, thecross-talk prevention ring comprising a conductive material.
 2. Thesemiconductor chip of claim 1 further comprising a seal ring adjacent toedges of the semiconductor chip, wherein the seal ring encircles thecross-talk prevention ring, and wherein the TSV is between the seal ringand the cross-talk prevention ring.
 3. The semiconductor chip of claim 2further comprising a sacrificial ring between the seal ring and theedges of the semiconductor chip.
 4. The semiconductor chip of claim 2further comprising a plurality of TSVs between the seal ring and thecross-talk prevention ring.
 5. The semiconductor chip of claim 1,wherein the cross-talk prevention ring encircles an additional TSV. 6.The semiconductor chip of claim 1 further comprising a seal ringadjacent to edges of the semiconductor chip, wherein the cross-talkprevention ring comprises a seal ring extension and a portion of theseal ring.
 7. The semiconductor chip of claim 6, wherein the cross-talkprevention ring comprises a corner portion of the seal ring.
 8. Thesemiconductor chip of claim 6, wherein the cross-talk prevention ringcomprises an edge and two corner portions of the seal ring.
 9. Thesemiconductor chip of claim 1, wherein the cross-talk prevention ringcomprises a second portion in the semiconductor substrate, and whereinthe second portion is conductive and is electrically connected to thefirst portion.
 10. The semiconductor chip of claim 1, wherein thecross-talk prevention ring comprises a second portion in thesemiconductor substrate, and wherein the second portion comprises adielectric material.
 11. The semiconductor chip of claim 1, wherein thecross-talk prevention ring is grounded.
 12. The semiconductor chip ofclaim 1 further comprising a plurality of TSVs, each encircled by anadditional grounded cross-talk prevention ring.
 13. The semiconductorchip of claim 1, further comprising a seal ring comprising four sides,each being adjacent to an edge of the semiconductor chip, wherein thecross-talk prevention ring is encircled by the seal ring, wherein thecross-talk prevention ring comprises four sides, each being adjacent toone of the sides of the seal ring, wherein the cross-talk preventionring is grounded, and wherein the TSV is located in a region between theseal ring and the cross-talk prevention ring.
 14. The semiconductor chipof claim 13, wherein the region between the seal ring and the cross-talkprevention ring is substantially free from active devices.
 15. Thesemiconductor chip of claim 13 further comprising a plurality of TSVsdistributed in the region between the seal ring and the cross-talkprevention ring.
 16. The semiconductor chip of claim 13, wherein thecross-talk prevention ring comprises a second portion in thesemiconductor substrate, and wherein the second portion is conductiveand is electrically connected to the first portion.
 17. Thesemiconductor chip of claim 13, wherein the cross-talk prevention ringcomprises a second portion in the semiconductor substrate, and whereinthe second portion comprises a dielectric material.
 18. Thesemiconductor chip of claim 1, further comprising a seal ring comprisingfour sides, each being adjacent to an edge of the semiconductor chip;and a seal ring extension comprising a first end and a second end, eachphysically connected to a portion of the seal ring, wherein the sealring extension and the seal ring form the cross-talk prevention ringencircling a first region of the semiconductor die, and wherein thefirst region is substantially free from active devices, the TSV beinglocated in the first region, a second region outside the cross-talkprevention ring comprising active devices.
 19. The semiconductor chip ofclaim 18, wherein the first region further comprises additional TSVs.